Hybrid materials employing PPE/polystyrene/curable epoxy mixtures

ABSTRACT

A curable melt blended composition and a method of making the composition by melt blending a thermoplastic polymer comprising polyphenylene ether (PPE) polymer and a polystyrene polymer, preferably high impact polystyrene (HIPS), and optionally a compatiblizer, with an uncured epoxy component, comprising a curable epoxy and an epoxy curing agent, at a temperature greater than 150° C. and without addition of solvent wherein the epoxy component of the resulting curable melt blended composition remains substantially uncured.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. Ser. No. 10/319,953, filed Dec.16, 2002, issued as U.S. Pat. No. 6,787,605, which was a divisional ofU.S. Ser. No. 09/025,400, filed Feb. 18, 1998, issued as U.S. Pat. No.6,518,362, the disclosure of which is herein incorporated by reference.

FIELD OF THE INVENTION

This invention relates to methods for making curable melt processedmaterials comprising mixtures of polyphenylene ether (PPE) andpolystyrene (PS), particularly high impact polystyrene (HIPS), withuncured epoxy components which comprise a curable epoxy and an epoxycuring agent, curable materials made by this method, and materialsresulting from the subsequent cure of those materials.

BACKGROUND OF THE INVENTION

It is a common practice in the industry to blend a small amount ofelastomeric or thermoplastic material into a hard thermosetting resin inorder to toughen (i.e., increase the ductility of) the thermoset.Elastomeric or thermoplastic toughening agents include natural rubbers,polyolefins, and vinyl copolymers such as poly(styrene-co-butadiene). Insuch cases, the toughening agent is blended in a ratio of from about1:20 to about 1:4 with a curable thermosetting resin such that thethermoplastic component becomes the dispersed phase in a thermosettingresin continuous phase.

U.S. Pat. No. 5,709,948 discloses curable mixtures of polyolefin resinsand epoxies. Curable mixtures comprising PPEs are not disclosed.

EP 592,145 and U.S. Pat. No. 4,912,172 disclose curable compositionsconsisting essentially of a polyphenylene ether (PPE), an epoxy, a zincor aluminum catalyst, and, in some cases, an imide co-catalyst. Thesereferences do not teach that a curable melt processed composition ofgreater than 50% thermoplastic can be obtained. These referencesdisclose solvent mixing of the components or mixing wherein a liquidepoxy is the major component. These references do not teach the use of aPPE/HIPS blend thermoplastic. These references disclose materials forstructural use rather than for use as adhesives or coatings.

U.S. Pat. No. 5,001,010 discloses a curable article comprising a mixtureof an epoxy and an epoxy cure catalyst with a specific PPE obtained bymelt processing the PPE at 230° C.-290° C. prior to addition of epoxy.This reference discloses solvent mixing of the epoxy with themelt-processed PPE and subsequent cure at 190° C.-250° C.

U.S. Pat. No. 5,308,565 discloses a prepreg board made with reinforcingfiber and a curable composition which preferably comprises PPE, a liquidepoxy, a flame retardant, and a curing catalyst, but at least comprisingthe first two elements. The blend is partially cured during mixing ('565at col. 2, ln. 50) at 100-130° C., so that it can be granulated andmixed with a substrate for final curing to form a mat. The referenceemphasizes throughout that the mixing is performed at 100-130° C. Thereference recommends an epoxy content of greater than 50%. ('565 at col.13, ln. 31). This reference discloses materials for structural userather than for use as adhesives or coatings.

EP 137,545 discloses an article made from a blend of PPE, HIPS and anepoxy resin which is coated with a lacquer or adhesive. The material ofthe reference is required to receive a coating or adhesive and is notdisclosed as being suitable for use as a coating or adhesive. Thereference does not teach that the epoxy component is cured or uncured atany point. The reference does not teach curing the epoxy component orthe inclusion of any curative or catalyst.

Venderbosch, Nelissen, Meijer and Lemstra, Makromol. Chem., Macromol.Symp. 75, pp. 73-84 (1993); Venderbosch, Meijer and Lemstra, POLYMER,Vol. 35, no. 20, pp. 4349-4357 (1994); and Venderbosch, Meijer andLemstra, POLYMER, Vol. 36, no. 6, pp. 1167-1178 (1995) disclose meltmixing combinations of PPE and epoxy monomers. These references do notdescribe PPE/PS/epoxy mixtures nor the use of compatiblizers with suchmixtures.

SUMMARY OF THE INVENTION

Briefly, the present invention provides a method of making a curablemelt blended composition by melt blending 60 to 99.9 weight percent of athermoplastic component, comprising 1-99 weight percent of polyphenyleneether (PPE) polymer, and 1-99 weight percent of polystyrene polymer,preferably high impact polystyrene (HIPS) polymer; and 0.1 to 40 weightpercent of an uncured epoxy component, comprising a curable epoxy and aneffective amount of a curing agent for said curable epoxy, where meltblending occurs at a temperature greater than 150° C. and is achievedwithout addition of solvent and the epoxy component of the resultingcomposition is substantially uncured.

In another aspect, the present invention provides a curable melt blendedcomposition comprising 60 to 99.9 weight percent of a thermoplasticcomponent, comprising 1-99 weight percent of polyphenylene ether (PPE)polymer, and 1-99 weight percent of polystyrene polymer, preferably highimpact polystyrene (HIPS) polymer; and 0.1 to 40 weight percent of anuncured epoxy component, comprising a curable epoxy and an effectiveamount of a curing agent for said curable epoxy, wherein the epoxycomponent of the resulting composition is substantially uncured.

In another aspect, the present invention provides a cured materialresulting from the heat or light cure of the curable melt blendedcomposition provided herein.

In another aspect, the present invention provides an adhesive or coatingcomprising the curable melt blended composition provided herein or thecured material resulting from the heat or light cure of the curable meltblended composition provided herein.

What has not been described in the art, and is provided by the presentinvention, is a curable melt processed composition of PPE/polystyrene,epoxy and an epoxy curative, and, optionally, a compatibilizer, whereinthe thermoplastic is the major component. In particular, the art doesnot disclose or teach the method, or the resulting material, whereinPPE/PS, epoxy and epoxy curing agent and, optionally, a compatibilizer,are combined by melt processing, without solvent, at greater than 150°C., to result in a curable composition wherein the epoxy componentremains substantially uncured. Furthermore, the art does not disclose oranticipate the improved peel and overlap shear strengths exhibited bythe PPE/PS/epoxy blends relative to PPE/epoxy blends.

In this application:

“curing agent”, for epoxy, means an epoxy curative or an epoxy catalyst;

“does not substantially heat cure”, used in regard to a compositioncontaining an epoxy component, means remains substantially uncured,

“substantially uncured” means at least half of the reactive sites forpolymerization in a population of monomeric units remain unreacted,preferably more than about 90% remain unreacted and most preferably morethan about 95% remain unreacted, and

“substituted” means substituted by conventional substituents which donot interfere with the desired product, e.g., substituents can be alkyl,alkoxy, aryl, phenyl, halo (F, Cl, Br, I), cyano, nitro, etc.

It is an advantage of the present invention to provide a method formaking materials which exhibit improved peel strength, shear strengthand modulus at high temperatures. It is a further advantage to providesuch a material in a curable state, which may be applied as an adhesiveor coating before cure. It is a further advantage to provide suchmaterial which is suitable for uses as an adhesive in electronicsapplications.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a plot of storage modulus versus temperature obtained bydynamic mechanical analysis of a material of the present invention, incured (A) and uncured (B) state, and a comparative example (C).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides a curable melt blended compositioncomprising 60 to 99.9 weight percent of a thermoplastic polymercomprising 1-99 weight percent of polyphenylene ether (PPE) polymer and1-99 weight percent of polystyrene polymer, preferably high impactpolystyrene (HIPS) polymer; and 0.1 to 40 weight percent of an uncuredepoxy component comprising a curable epoxy and an effective amount ofcuring agent for the epoxy, wherein the epoxy component of thecomposition is substantially uncured.

The thermoplastic component includes 1-99% by weight of a polyphenyleneether polymer (PPE). The polyphenylene ethers (also known aspolyphenylene oxides or PPOs) used in the present invention are awell-known class of polymers. They are widely used in industry,especially as engineering plastics in applications requiring toughnessand heat resistance.

The polyphenylene ethers comprise a plurality of structural units havingthe formula:

In each of said units independently, each Q¹ is independently halogen,primary or secondary lower alkyl (i.e., alkyl containing up to 7 carbonatoms), phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, orhalohydrocarbonoxy wherein at least two carbon atoms separate thehalogen and oxygen atoms; and each Q² is independently hydrogen,halogen, primary or secondary lower alkyl, phenyl, haloalkyl,hydrocarbonoxy or halohydrocarbonoxy as defined for Q¹. Examples ofsuitable primary lower alkyl groups are methyl, ethyl, n-propyl,n-butyl, isobutyl, n-amyl, isoamyl, 2-methylbutyl, n-hexyl,2,3-dimethylbutyl, 2-,3- or 4-methylpentyl and the corresponding heptylgroups. Examples of secondary lower alkyl groups are isopropyl,sec-butyl and 3-pentyl. Preferably, any alkyl radicals are straightchain rather than branched. Most often, each Q¹ is alkyl or phenyl,especially C₁₋₄ alkyl, and each Q² is hydrogen.

Both homopolymer and copolymer polyphenylene ethers are within thepurview of the process of the present invention. Suitable homopolymersare those containing, for example, 2,6-dimethyl-1,4-phenylene etherunits. Suitable copolymers include random copolymers containing suchunits in combination with, for example, 2,3,6-trimethyl-1,4-phenyleneether units. Many suitable random copolymers, as well as homopolymers,are disclosed in the patent literature. Reference is made to U.S. Pat.Nos. 4,054,553, 4,092,294, 4,477,649, 4,477,651 and 4,517,341, thedisclosures of which are incorporated by reference herein.

A preferred PPE, poly(2,6-dimethylphenylene oxide), is available underthe trade name Blendex™ HPP820 from General Electric Co., Pitsfield,Mass.

The thermoplastic component may include 1-99% by weight of a polystyrenepolymer, but preferably 1-90% and more preferably 10-90% by weight.Polystyrene polymers are well known in the art. The polystyrene mayoptionally be substituted at any available position. Preferably, thepolystyrene polymer is a high impact polystyrene polymer (HIPS).Thermoplastic high impact polystyrene polymers (HIPS) are well known inthe art, as are PPE/HIPS blends. Preferred PPE/HIPS blends are availablefrom General Electric Co., Pitsfield, Mass., under the trade nameNoryl™. It is believed that Noryl™ EN185 comprises approximately 10% PPEand 90% HIPS and Noryl™ SE1X comprises approximately 50% PPE and 50%HIPS. The T_(g) and heat deflection temperature (HDT) of PPE/HIPS blendsare determined by the relative amount of PPE to HIPS, with T_(g) and HDTincreasing in proportion to PPE content. Noryl™ EN185, Noryl™ SE1X, andBlendex™ HPP820 have HDT's (at 264 psi) of 82, 118, and 182° C.,respectively.

The thermoplastic component may optionally include greater than 0% byweight to about 25% by weight, preferably 1-15% and more preferably1-110% by weight, of a functionalized polystyrene as a compatiblizer forthe thermoplastic and epoxy components and to promote adhesion of thecured composition to a substrate. The functionalized polystyrene can bemixed with the thermoplastic polymer blend prior to mixing with theepoxy or can be added during melt blending of the thermoplastic andepoxy.

Suitable functionalized polystyrenes are polystyrenes that haveadditional chemical functionality, obtained through eithercopolymerization of styrene monomer with a functional monomer or graftcopolymerization subsequent to styrene polymerization. Typically, suchfunctionalized groups include O, N, S, P, or halogen heteroatoms.Reactive functionalized groups include carboxylic acid, hydroxyl, amide,nitrile, carboxylic acid anhydride, epoxide, or halogen groups. Manyfunctionalized polystyrenes are available commercially, such asstyrene-maleic anhydride (SMA) copolymers, styrene-acrylonitrile (SAN)copolymers, and copolymers of styrene with, e.g. N-alkyl or N-arylmaleimides, such as N-phenyl maleimide; fumaronitrile or maleonitrile;and methyl methacrylate. Commercially available SMA copolymers includethe Dylark™ family, such as Dylark™ 332 (Nova Chemicals, Sarnia,Ontario, Canada), the Cadon™ family, such as Cadon™ 135 (Bayer Corp.,Pittsburgh, Pa.), and the Sapron™ S family, such as Sapron™ SM 300 (DSMEngineering Plastics North America, Northbrook, Ill.). Commerciallyavailable SAN copolymers include Luran™ polymers (BASF Corp., PlasticMaterials, Mt. Olive, N.J.).). Any functionalized block copolymerscomprising styrene can be useful as compatibilizers in the presentinvention, including, for example, maleated Kraton™ polymers (ShellChemical Co., Houston, Tex.).

The blend comprises 0.1-40% by weight, but preferably 1-30% and morepreferably 1-20% by weight, of an epoxy component comprising athermosettable epoxy resin. The thermosettable epoxy resins of theinvention preferably comprise compounds which contain one or more 1,2-,1,3- and 1,4-cyclic ethers, which also may be known as 1,2-, 1,3- and1,4-epoxides. The 1,2-cyclic ethers are preferred. Such compounds can besaturated or unsaturated, aliphatic, alicyclic, aromatic orheterocyclic, or can comprise combinations thereof. Compounds thatcontain more than one epoxy group (i.e., polyepoxides) are preferred.

Aromatic polyepoxides (i.e., compounds containing at least one aromaticring structure, e.g., a benzene ring, and more than one epoxy group)that can be used in the present invention include the polyglycidylethers of polyhydric phenols, such as Bisphenol A-type resins and theirderivatives, epoxy cresol-novolac resins, Bisphenol-F resins and theirderivatives, and epoxy phenol-novolac resins; and glycidyl esters ofaromatic carboxylic acids, e.g., phthalic acid diglycidyl ester,isophthalic acid diglycidyl ester, trimellitic anhydride trigylcidylester, and pyromellitic acid tetraglycidyl ester, and mixtures thereof.Preferred aromatic polyepoxides are the polyglycidyl ethers ofpolyhydric phenols, such as the EPON™ series of diglycidyl ethers ofBisphenol-A, including EPON 828 and EPON 1001F, available commerciallyfrom Shell Chemicals, Inc., Houston, Tex.

Representative aliphatic cyclic polyepoxides (i.e., cyclic compoundscontaining one or more saturated carbocyclic rings and more than oneepoxy group, also known as alicyclic compounds) useful in the presentinvention include the “ERL™” series of alicyclic epoxides commerciallyavailable from Union Carbide Corp., Danbury, Conn., such as vinylcyclohexene dioxide (ERL-4206),3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (ERL-4221),3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate (ERL-4201), bis(3,4-epoxy-6-methylcycylohexylmethyl)adipate(ERL-4289), dipentene dioxide (ERL-4269), as well as2-(3,4-epoxycyclohexyl-5,1″-spiro-3″,4″-epoxycyclohexane-1,3-dioxane,4-(1,2-epoxyethyl)-1,2-epoxycyclohexane and2,2-bis(3,4-epoxycyclohexyl)propane. Preferred alicyclic polyepoxidesare the ERL™ series.

Representative aliphatic polyepoxides (i.e., compounds containing nocarbocyclic rings and more than one epoxy group) include1,4-bis(2,3-epoxypropoxy)butane, polyglycidyl ethers of aliphaticpolyols such as glycerol, polypropylene glycol, 1,4-butanediol, and thelike, and the diglycidyl ester of linoleic dimer acid.

A wide variety of commercial epoxy resins are available and are listedor described in, e.g., the Handbook of Epoxy Resins, by Lee and Neville,McGraw-Hill Book Co., New York (1967), Epoxy Resins, Chemistry andTechnology, Second Edition, C. May, ed., Marcell Decker, Inc., New York(1988), and Epoxy Resin Technology, P. F. Bruins, ed., IntersciencePublishers, New York, (1968). Any of the epoxy resins described thereinmay be useful in preparation of the materials of the present invention.

Suitable curatives or catalysts should tolerate the melt processing stepaccording to the present invention without substantially curing theepoxy component, while retaining the ability to cure the epoxy componentat a later time under the influence of heat or light. More specifically,the epoxy should remain substantially uncured after exposure to thetemperature present in the melt processing step for the duration of themelt processing step. Other factors that influence catalyst selectioninclude the thickness of the film to be cured, transparency of the filmto curing radiation, and the film's end use (for example, when the finaluse of the film occurs after orientation or stretching, use of a thermalcatalyst may not be appropriate, since the thermal activation maycompromise the degree of orientation or the structural integrity of thestretched film). Subject to these limitations, suitable curatives may beselected from any known catalysts.

Curatives of the present invention can be photocatalysts or thermalcuring agents.

Known photocatalysts include two general types: onium salts and cationicorganometallic salts, which are both useful in the invention.

Onium salt photocatalysts for cationic polymerizations include iodoniumand sulfonium complex salts. Useful aromatic iodonium complex salts areof the general formula:

wherein

Ar¹ and Ar² can be the same or different and are aromatic groups havingfrom 4 to about 20 carbon atoms, and are selected from the groupconsisting of phenyl, thienyl, furanyl, and pyrazolyl groups;

Z is selected from the group consisting of oxygen, sulfur, acarbon-carbon bond,

wherein R can be aryl (having from 6 to about 20 carbon atoms, such asphenyl) or acyl (having from 2 to about 20 carbon atoms, such as acetyl,or benzoyl), and

wherein R₁ and R₂ are selected from the group consisting of hydrogen,alkyl radicals having from 1 to about 4 carbon atoms, and alkenylradicals having from 2 to about 4 carbon atoms;

m is zero or 1; and

X may have the formula DQ_(n), wherein D is a metal from Groups IB toVIII or a metalloid from Groups IIIA to VA of the Periodic Chart of theElements (Chemical Abstracts version), Q is a halogen atom, and n is aninteger having a value of from 1 to 6. Preferably, the metals arecopper, zinc, titanium, vanadium, chromium, magnesium, manganese, iron,cobalt, or nickel and the metalloids preferably are boron, aluminum,antimony, tin, arsenic and phosphorous. Preferably, the halogen, Q, ischlorine or fluorine. Illustrative of suitable anions are BF₄ ⁻, PF₆ ⁻,SbF₆ ⁻, FeCl₄ ⁻, SnCl₅ ⁻, AsF₆ ⁻, SbF₅OH⁻, SbCl₆ ⁻, SbF₅ ⁻², AlF₅ ⁻²,GaCl₄ ⁻, InF₄ ⁻, TiF₆ ⁻², ZrF₆ ⁻, CF₃SO₃ ⁻, and the like. Preferably,the anions are BF₄ ⁻, PF₆ ⁻, SbF₆ ⁻, AsF₆ ⁻, SbF₅OH⁻, and SbCl₆ ⁻. Morepreferably, the anions are SbF₆ ⁻, AsF₆ ⁻, and SbF₅OH⁻.

Additional anions useful as the anionic portion of the catalysts andinitiators of the present invention have been described in U.S. Pat. No.5,554,664, incorporated herein by reference. The anions may be generallyclassified as fluorinated (including highly fluorinated andperfluorinated) tris alkyl- or arylsulfonyl methides and correspondingbis alkyl- or arylsulfonyl imides, as represented by Formulas X and Y,respectively, and hereinafter referred to as “methide” and “imide”anions, respectively, for brevity,(R_(f) SO₂)₃C⁻  (X)(R_(f) SO₂)₂N⁻  (Y)

wherein each R_(f) is independently selected from the group consistingof highly fluorinated or perfluorinated alkyl or fluorinated arylradicals. The methides and imides may also be cyclic, when a combinationof any two R_(f) groups are linked to form a bridge.

The R_(f) alkyl chains may contain from 1-20 carbon atoms, with 1-12carbon atoms preferred. The R_(f) alkyl chains may be straight,branched, or cyclic and preferably are straight. Heteroatoms or radicalssuch as divalent oxygen, trivalent nitrogen or hexavalent sulfur mayinterrupt the skeletal chain, as is well recognized in the art. WhenR_(f) is or contains a cyclic structure, such structure preferably has 5or 6 ring members, 1 or 2 of which can be heteroatoms. The alkyl radicalR_(f) is also free of ethylenic or other carbon-carbon unsaturation:e.g., it is a saturated aliphatic, cycloaliphatic or heterocyclicradical. By “highly fluorinated” is meant that the degree offluorination on the chain is sufficient to provide the chain withproperties similar to those of a perfluorinated chain. Moreparticularly, a highly fluorinated alkyl group will have more than halfthe total number of hydrogen atoms on the chain replaced with fluorineatoms. Although hydrogen atoms may remain on the chain, it is preferredthat all hydrogen atoms be replaced with fluorine to form aperfluoroalkyl group, and that any hydrogen atoms beyond the at leasthalf replaced with fluorine that are not replaced with fluorine bereplaced with bromine and or chlorine. It is more preferred that atleast two out of three hydrogens on the alkyl group be replaced withfluorine, still more preferred that at least three of four hydrogenatoms be replaced with fluorine and most preferred that all hydrogenatoms be replaced with fluorine to form a perfluorinated alkyl group.

The fluorinated aryl radicals of Formulas 2a and 2b may contain from 6to 22 ring carbon atoms, preferably 6 ring carbon atoms, where at leastone, and preferably at least two, ring carbon atoms of each aryl radicalis substituted with a fluorine atom or a highly fluorinated orperfluorinated alkyl radical as defined above, e.g., CF₃.

Examples of anions useful in the practice of the present inventioninclude: (C₂F₅SO₂)₂N⁻, (C₄F₉SO₂)₂N⁻, (C₈F₁₇SO₂)₃C⁻, (CF₃SO₂)₃C⁻,(CF₃SO₂)₂N⁻, (C₄F₉SO₂)₃C⁻, (CF₃SO₂)₂(C₄F₉SO₂)C⁻, (CF₃SO₂)(C₄F₉SO₂)N⁻,[(CF₃)₂NC₂F₄SO₂]₂N⁻, (CF₃)₂NC₂F₄SO₂C⁻(SO₂CF₃)₂,(3,5-bis(CF₃)C₆H₃)SO₂N⁻SO₂CF₃,

C₆F₅SO₂C⁻(SO₂CF₃)₂ C₆F₅SO₂N⁻SO₂CF₃ and the like. More preferred anionsare those described by Formula X wherein R_(f) is a perfluoroalkylradical having 1-4 carbon atoms.

The Ar₁ and Ar₂ aromatic groups may optionally comprise one or morefused benzo rings (e.g., naphthyl, benzothienyl, dibenzothienyl,benzofuranyl, dibenzofuranyl, etc.). The aromatic groups may also besubstituted, if desired, by one or more non-basic groups if they areessentially non-reactive with epoxide and hydroxyl functionalities.

Useful aromatic iodonium complex salts are described more fully in U.S.Pat. No. 4,256,828, which is incorporated herein by reference.

The aromatic iodonium complex salts useful in the invention arephotosensitive only in the ultraviolet region of the spectrum. However,they can be sensitized to the near ultraviolet and the visible range ofthe spectrum by sensitizers for known photolyzable organic halogencompounds. Illustrative sensitizers include aromatic amines and coloredaromatic polycyclic hydrocarbons, as described in U.S. Pat. No.4,250,053, incorporated herein by reference.

Aromatic sulfonium complex salt catalysts suitable for use in theinvention are of the general formula

wherein

R₃, R₄ and R₅ can be the same or different, provided that at least oneof the groups is aromatic. These groups can be selected from the groupconsisting of aromatic moieties having from 4 to about 20 carbon atoms(e.g., substituted and unsubstituted phenyl, thienyl, and furanyl) andalkyl radicals having from 1 to about 20 carbon atoms. The term “alkyl”includes substituted alkyl radicals (e.g., substituents such as halogen,hydroxy, alkoxy, and aryl). Preferably, R₃, R₄ and R₅ are each aromatic;and

Z, m and X are all as defined above with regard to the iodonium complexsalts.

If R₃, R₄ or R₅ is an aromatic group, it may optionally have one or morefused benzo rings (e.g., naphthyl, benzothienyl, dibenzothienyl,benzofuranyl, dibenzofuranyl, etc.). The aromatic groups may also besubstituted, if desired, by one or more non-basic groups if they areessentially non-reactive with epoxide and hydroxyl functionalities.

Triaryl-substituted salts such as triphenylsulfoniumhexafluoroantimonate and p-(phenyl(thiophenyl))diphenylsulfoniumhexafluoroantimonate are preferred sulfonium salts. Triphenylsulfoniumhexafluoroantimonate (Ph₃SSbF₆) is a most preferred catalyst. Usefulsulfonium salts are described more fully in U.S. Pat. No. 5,256,828.

Aromatic sulfonium complex salts useful in the invention arephotosensitive only in the ultraviolet region of the spectrum. However,they can be sensitized to the near ultraviolet and the visible range ofthe spectrum by a select group of sensitizers such as described in U.S.Pat. Nos. 4,256,828 and 4,250,053.

Suitable photoactivatable organometallic complex salts useful in theinvention include those described in U.S. Pat. Nos. 5,059,701,5,191,101, and 5,252,694, each of which is incorporated herein byreference. Such salts of organometallic cations have the generalformula:[(L¹)(L²)M^(m)]^(+e)X⁻wherein M^(m) represents a metal atom selected from elements of periodicgroups IVB, VB, VIB, VIIB and VIII, preferably Cr, Mo, W, Mn, Re, Fe,and Co; L¹ represents none, one, or two ligands contributing π-electronsthat can be the same or different ligand selected from the groupconsisting of substituted and unsubstituted acyclic and cyclicunsaturated compounds and groups and substituted and unsubstitutedcarbocyclic aromatic and heterocyclic aromatic compounds, each capableof contributing two to twelve π-electrons to the valence shell of themetal atom M. Preferably, L¹ is selected from the group consisting ofsubstituted and unsubstituted η³-allyl, η⁵-cyclopentadienyl,η⁷-cycloheptatrienyl compounds, and η⁶-aromatic compounds selected fromthe group consisting of η⁶-benzene and substituted η⁶-benzene compounds(e.g., xylenes) and compounds having 2 to 4 fused rings, each capable ofcontributing 3 to 8 π-electrons to the valence shell of M^(m); L²represents none or 1 to 3 ligands contributing an even number ofσ-electrons that can be the same or different ligand selected from thegroup consisting of carbon monoxide, nitrosonium, triphenyl phosphine,triphenyl stibine and derivatives of phosphorous, arsenic and antimony,with the proviso that the total electronic charge contributed to M^(m)by L¹ and L² results in a net residual positive charge of e to thecomplex; and e is an integer having a value of 1 or 2, the residualcharge of the complex cation; X is a halogen-containing complex anion,as described above.

Certain thermally-activated curing agents for epoxy resins (e.g.,compounds that effect curing and crosslinking of the epoxide by enteringinto a chemical reaction therewith) can be useful in the presentinvention. Preferably, such curing agents are thermally stable attemperatures at which mixing of the components takes place.

Suitable thermal curing agents include aliphatic and aromatic primaryand secondary amines, e.g., di(4-aminophenyl)sulfone,di(4-aminophenyl)ether, and 2,2-bis-(4-aminophenyl)propane; aliphaticand aromatic tertiary amines, e.g., dimethylaminopropylamine andpyridine; quaternary ammonium salts, particularly pyridinium salts suchas N-methyl-4-picolinium hexafluorophosphate; sulfoninum salts; fluorenediamines, such as those described in U.S. Pat. No. 4,684,678,incorporated herein by reference; boron trifluoride complexes such asBF₃.Et₂O and BF₃.H₂C₂H₅OH; imidazoles, such as methylimidiazole;hydrazines, such as adipohydrazine; and guanidines, such astetramethylguanidine and dicyandiamide (cyanoguanimide, commonly knownas DiCy). It is to be understood that a careful choice among thesecuring agents must be made, since many of them would be unsuitable foruse when high-melting PPE/HIPS materials are present, but that they maybe useful in preparing mixtures of the invention that compriselow-melting thermoplastic materials and epoxy resins.

Additional high temperature thermal epoxy catalysts that can beparticularly useful in the present invention include simple pyridinium,quinolinium, indolinium, benzothiazolium, alkyl, aryl and alkylarylammonium, sulfonium and phosphonium salts. These are effectiveinitiators of the cationic polymerization of epoxies in the 250-350° C.temperature range. Because of these high exotherm temperatures, thesecatalysts are particularly suited to use with extrusion temperatures of200° C. or greater. The compositions are stable in the extruder (i.e.,they do not cure), eliminating problems that would be caused bycrosslinking during this processing step. When finally cured, thesecompositions give surprisingly high overlap shear bond strengths. Usefulammonium and phosphonium salts are described in copending applicationU.S. Ser. No. 08/782,476, the teachings of which are incorporated hereinby reference.

Catalysts useful in the invention can be present in an amount in therange of 0.01 to 10 weight percent, based on total epoxy resincomposition, preferably 0.01 to 5 weight percent, and most preferably0.5 to 3 weight percent. Catalysts may be added to the chosen epoxy in apowder form at temperatures up to about 150° C. No solvent is necessaryfor this operation. Incorporation time can range from 10-20 minutesdepending on the epoxy/catalyst system. The epoxy/catalyst may then bepumped into the extruder for the melt processing step. Alternatively,the catalyst could be added directly into the thermoplastic/epoxymixture during melt blending.

Various adjuvants can also be added to the compositions of the inventionto alter the physical characteristics of the final material. Includedamong useful adjuvants are thixotropic agents such as fumed silica;pigments to enhance color tones such as ferric oxide, carbon black andtitanium dioxide; fillers such as mica, silica, acicular wollastonite,calcium carbonate, magnesium sulfate and calcium sulfate; electricallyand/or thermally conductive fillers, including metal particles,graphite, and metal-coated microspheres; chopped fibers and whiskers,including glass and carbon; clays such as bentonite; glass beads andbubbles; reinforcing materials such as unidirectional woven and nonwovenwebs of organic and inorganic fibers such as polyester, polyimide, glassfibers, polyamides such as poly(p-phenylene terephthalamide), carbonfibers, and ceramic fibers. Amounts up to about 200 parts of adjuvantper 100 parts of PPE/PS/epoxy composition can be used.

The materials of the present invention can be prepared by batch orcontinuous processing.

Batch processing can be accomplished by adding solid thermoplastic,typically in pellet form, to a preheated mixer, such as a Brabendermixer (C. W. Brabender Instruments, Inc., South Hackensack, N.J.)equipped with, e.g., cam or sigma blades. After stirring for about 5minutes, the thermoplastic is melted and a mixture of epoxy and curativefor the epoxy is added with continued stirring. The resultant mixture isstirred to ensure complete mixing, at a duration and temperature belowthat which would substantially cure the epoxy component, and removedfrom the mixer while still molten. The mixture can then be molded,formed, shaped or pressed into a desired final configuration. The shapedobject may then be irradiated and/or heated to cure the epoxy resincomponent. In particular, when a thin sheet or film is desired, themolten mass can be pressed in a heated flat-plate press, such as aCarver laboratory press (F. Carver, Inc., Wabash, Ind.).

Continuous processing can be accomplished using an extruder, e.g., atwin-screw extruder, equipped with a downstream port, a static mixer andan appropriate output orifice (film die, sheet die, fiber die, profiledie, etc.) and a take-up or casting roll and wind-up roll(s), asappropriate. The casting roll may be cooled or maintained at a settemperature by thermostatic means. Solid thermoplastic is added to theinput end of the extruder and processed using a temperature profile thatis appropriate for the thermoplastic and which will not substantiallycure the epoxy component, taking into account the duration of residenceof the material in the extruder during processing. The epoxy componentmay be injected via gear or syringe pump. Take-up line speed is adjustedas appropriate for the output (sheet, fiber, etc.), typically from about0.5 m/min to about 200 m/min.

In the cases where thermal curing of the epoxy is desirable immediatelyafter extrusion, i.e., before the thermoplastic polymer cools andsolidifies, further heating of the extrudate can take place directly atthe die orifice or at a casting wheel. When it is desired that epoxycure take place after the thermoplastic polymer cools and solidifies,the heat source(s) can be located just prior to the take-up roll.Finally, when it is desirable that no epoxy curing take place afterextrusion such heating devices are absent.

In the case where photocuring of the epoxy is desirable immediatelyafter extrusion, i.e., before the thermoplastic polymer cools andsolidifies, UV irradiation of the heated extrudate can take placedirectly at the die orifice. Irradiation can be accomplished by anynumber of commercially-available UV sources, such as one or more FusionSystems D or H bulbs (available from Fusion UV Curing Systems,Rockville, D) or Sylvania BL 350 bulbs. When it is desired that epoxycure take place after the thermoplastic polymer cools and solidifies,the light source(s) can be located just prior to the take-up roll.Finally, where it is desirable that no immediate epoxy curing take placeafter extrusion, the irradiation devices are absent and precautions maybe taken to prevent UV exposure.

It is within the scope of the invention that a blended film, obtainedfrom a sheet die, may be drawn either uniaxially or biaxially as itemerges from the die. Cure, as above, may take place before, during orafter such drawing.

Where a film is used as an adhesive or coating, the material may beapplied to its final substrate in an uncured state as a sheet and curedin situ by application of heat, pressure, UV light, or combinationsthereof.

This invention is useful in the production of high performance adhesivesand coatings, especially where improved peel strength is required. Forexample, this invention is useful in laminating films for electronicapplications. The present invention is useful as an adhesive, as aprotective covercoat, or as both.

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention.

EXAMPLES

A variety of materials according to the present invention were made andare discussed in the following examples. Table A discloses the startingmaterials and weight proportions used in each example. Table A alsodiscloses peel strength values for examples where that value wasmeasured. Examples designated with a C, i.e., examples 1C, 13C, and21C-30C, are comparative examples.

TABLE A Composition and Peel Strength of Examples Functionalized PeelStrength PPE or Epoxy Polystyrene on Kapton E ™ PPE/HIPS (Epon Cata-(Dylark (ave. value) Ex # blend 828 ™) lyst 332 ™) (N/m)  1C  100% EN185— — — 18  5 95.6% EN185  4.4% S — 300  6 91.8% EN185  8.2% S — 330  791.2% EN185  8.8% S —  8 84.9% EN185 15.1% S — 0.0  9 78.9% EN185 21.1%S — 35 10   90% EN185 — —  10% 11   86% EN185  4.4% S 9.6% 320 12 82.3%EN185  8.5% S 9.2% 610 13C  100% SE1X — — — 18 14 94.9% SE1X  5.1% P —260 15 90.6% SE1X  9.4% P — 350 16 83.9% SE1X 16.1% P — 420 17 94.9%SE1X  5.1% S — 18 90.6% SE1X  9.4% S — 580 19 82.9% SE1X 17.1% S — 49020 81.6% SE1X  9.4% S 9.0% 21C  100% HPP820 — — — 18 22C 94.7% HPP820 5.3% P — 53 23C 90.2% HPP820  9.8% P — 35 24C 81.8% HPP820 18.2% P — 8825C 75.0% HPP820 25.0% P — 0.0 26C 70.0% HPP820 30.0% P — 0.0 27C 65.0%HPP820 35.0% P — 0.0 28C 57.0% HPP820 43.0% P — 0.0 29C 94.7% HPP820 5.3% S — 30C 87.8% HPP820 12.2% S —

Uncured materials were made according to the present invention by firstblending the epoxy with the catalyst and injecting this mixture via agear pump (Model HPB 4740, Zenith Metering pump, Parker Hannifin Co.,Sanford, N.C.) into a conical twin screw extruder (Haake, Paramus, N.J.)where the epoxy was mixed with the thermoplastic PPO or PPO/HIPS blendat a constant screw rate of 100 rpm. The mixture was extruded as a filmonto a casting wheel which was maintained at 20° C.

For compositions comprising Noryl EN185 and epoxy, the four extruderzones were each set at 200° C., with a pellet feed rate of 22.45 g/min,using a K-Tron™ feeder (K-Tron International, Pitman, N.J.). Typicalprocessing temperatures were 182-209-206-204° C., from back (pellet-feedend) to front (die end) of the extruder. Pressure at the front (tip) ofthe extruder prior to epoxy introduction was 7.93 MPa. The amount ofepoxy added was controlled by varying the speed of the metering pumpfrom 10 to 30 rpm.

For compositions comprising Noryl SE1X and epoxy (except Examples 18 and19), the extruder zones were set at 260-282-282-282° C., processingtemperatures were 288-279-285-281° C. from back to front, and the pelletfeed rate was 30 g/min. Initial pressure at the extruder tip was 7.6MPa. Metering pump speed was varied from 8 to 30 rpm. For Examples 18and 19, the extruder zones were set at 213-203-204-218° C. Processingtemperatures, from back to front, were 203-224-217-218° C. for Example18 and 195-213-208-218° C. for Example 19. The pellet feed rate was 24.2g/min. Initial pressure at the extruder tip was 13.1 MPa for Example 18and 8.6 MPa for Example 19. Metering pump speed was 13 rpm for Example18 and 26 rpm for Example 19.

For compositions comprising Blendex HPP820 and epoxy, the extruder zoneswere set at 260-288-288-288° C., processing temperatures were236-289-288-286° C., back to front, and the powder feed rate was 7.2g/min. Initial pressure at the extruder tip was 10.9 MPa. Metering pumpspeed was varied from 2 to 9 rpm.

Two catalysts were used, designated P and S: N-methyl-4-picoliniumhexafluorophosphate (P, described in copending application U.S. Ser. No.08/782,476, Example 6) and Ar₃SSbF₆ (S, where Ar can be phenyl, p-tolyl,or naphthyl; prepared as described in Example 2). N-methyl-4-picoliniumhexafluorophosphate (P) can be activated thermally, whereas Ar₃SSbF₆ (S)can be activated either thermally or photolytically. The catalysts wereadded to the epoxy in powder form, without solvent, at 80° C.Incorporation time ranged from 10-20 minutes depending on theepoxy/catalyst system. The resulting mixture contained about 2% byweight catalyst. The weight of catalyst is included in the weight of theepoxy in Table A. The epoxy used was Epon™ 828 (diglycidyl ether ofBisphenol A), available from Shell Chemicals, Inc., Houston, Tex.

The PPE and PPE/HIPS blends used were Noryl™ EN185 and Noryl™ SE1X,which are blends of poly(2,6-dimethylphenylene oxide) (PPO) and highimpact polystyrene (HIPS) (General Electric Plastics, Pittsfield,Mass.), and Blendex™ HPP820, which is PPO without admixed HIPS (GeneralElectric Plastics) It is estimated that the EN185 is approximately 10%PPO and 90% HIPS and the SE1X is approximately 50% PPO and 50% HIPS.Note that the T_(g) and heat deflection temperature (HDT) of PPO/HIPSblends are determined by the relative amount of PPO to HIPS, with T_(g)and HDT increasing in proportion to PPO content. Noryl™ EN185, Noryl™SE1X, and Blendex™ HPP820 have HDT's (at 1.8 MPa) of 82, 118, and 182°C., respectively.

In some examples, a functionalized polystyrene was mixed as acompatiblizer with the thermoplastic polymer blend prior to mixing withthe epoxy to improve compatibility of the thermoplastic and epoxycomponents. The material used, a coplymer of styrene and maleicanhydride, is sold under the trade name Dylark™ 332 (Nova Chemicals,Sarnia, Ontario, Canada), which can be dry blended with the PPE and/orPPE/HIPS pellets prior to blending with epoxy. However, it was foundthat compatibility of the PPE and PPE/HIPS blends with epoxy was verygood even without the added compatiblizer. No evidence of grossliquid-liquid separation occurred for any of the compositions of theexamples.

Peel strength tests were performed on 0.05 mm thick Kapton E films, apolyimide substrate used in flexible circuitry. The adhesive films ofthe examples were laminated between two pieces of Kapton E film suchthat approximately 5.0 cm of Kapton E extended beyond the lamination,for peel testing. The adhesive films were typically 0.025 mm thick,ranging from 0.012 mm to 0.51 mm thick, after lamination. Filmscomprising the S catalyst were laminated at 220° C. 3450 kPa for 50 min.and films comprising the P catalyst were laminated at 270° C., 3450 kPafor 50 min. Strips were cut from the laminates and 180° T-peels wereperformed on the test strips by fixing the two free Kapton E portions inthe jaws of an Instron tensile testing machine (Model 1122, InstronCorp., Park Ridge, Ill.), equipped with a 5 KN load cell, model2511-317, and using a crosshead speed of 0.64 cm/min. The average peelstrengths (5 trials) are presented in Table A. These results indicatethat peel strength rises dramatically with addition of epoxy until anoptimal level is reached. In addition, the data of Table A show that thePPE/PS/epoxy blends (Noryl™ EN185 and SE1X) exhibit more than 500%increase in peel strengths in comparison to PPE/epoxy blends (Noryl™HPP820).

Overlap shear strength tests were performed essentially according toASTM D11002-94 on three substrates: steel, aluminum and copper. Couponsof these materials measuring 11.43 cm×2.54 cm×3.2 mm were thoroughlycleaned with methyl ethyl ketone. Adhesive films of the invention,having thicknesses of from about 0.25 to about 0.75 mm were cut intosquares measuring 2.54 cm on a side and placed between two coupons suchthat the area of overlap was 6.45 cm². The coupons and sample were heldtogether with a small piece of high-temperature Teflon™ tape (Model5490, 3M, St. Paul, Minn.) and were heated under pressure in a Carverpress. The adhesives of examples 1C and 5 were cured at 220° C. and 3450kPa for 50 minutes. The adhesives of examples 13C, 15, 16, 21C and 24were cured at 270° C. and 3450 kPa for 50 minutes. Peak loads and strainto break were recorded from an Instron machine with a 44.5 KN load cell.The average values (5 repetitions) are presented in Table B. Theseresults indicate that the shear strength of the compositions of thepresent invention was markedly improved in most cases over comparativecompositions.

TABLE B Shear Strength on Three Substrates Steel Aluminum CopperThickness Load Extension Thickness Load Extension Thickness LoadExtension Ex # (mm) (MPa) (mm) (mm) (MPa) (mm) (mm) (MPa) (mm)  1C 0.1277.9 ± 2.1 6.35 ± 0.76 0.076 15.7 ± 4.2 3.05 ± 0.00 0.076 10.4 ± 2.2 2.03± 0.25  5 0.076 5.0 ± 2.5 4.07 ± 1.52 0.025 21.4 ± 0.8 3.56 ± 0.00 0.12725.6 ± 2.2 4.32 ± 1.27 13C 0.076 6.6 ± 2.8 2.03 ± 0.25 0.05 10.4 ± 1.92.79 ± 0.25 0.102  6.7 ± 1.2 3.05 ± 0.51 15 0.051 7.2 ± 2.5 2.03 ± 00  0.102 16.3 ± 2.8 3.05 ± 0.25 0.203  5.7 ± 1.5 3.81 ± 0.51 16 0.051 9.7 ±3.2 2.29 ± 0.51 0.076 17.4 ± 2.1 3.30 ± 0.25 0.203  8.6 ± 1.3 4.07 ±1.02 21C 0.076 1.9 ± 2.4 6.10 ± 0.76 0.076  1.6 ± 0.6 1.27 ± 0.25 0.102 2.1 ± 0.6 3.56 ± 0.25 24C 0.076 6.6 ± 1.1 1.52 ± 0.25 0.076  5.9 ± 1.52.03 ± 0.25 0.152  5.0 ± 1.2 2.79 ± 0.76

Dynamic Mechanical Analysis (DMA) tensile testing was performed on curedand uncured materials, resulting in plots of storage modulus (a measureof the sample stiffness) versus temperature. Free-standing sample stripsmeasuring 36 mm×6.4 mm×10 mm were used. The materials of the EN185-basedexamples were cured at 220° C. for 50 minutes and the materials of theSE1X and HPP820-based materials were cured at 270° C. for 50 minutes. ASeiko Instruments DMA 200 Rheometer (Seiko Instruments, Torrance,Calif.) equipped with a tensile sample feature was used. Separationbetween jaws was 20 mm. The temperature ramp was 2° C. per minute from−80 to 300° C., probed at 1 Hz.

A resulting plot is presented in FIG. 1. Curve A represents Example 15(9.4% Epon 828, containing P-Cat, in Noryl SE1X) after cure. Curve Brepresents Example 15 before cure. Curve C represents a comparativeexample, Example 13C, which is 100% Noryl SE1X.

The DMA test results were used to determine glass transitiontemperatures, shown in Table C. In general, the glass transitiontemperature of uncured materials was seen to decrease as more epoxy wasadded to the base thermoplastic. However, the glass transitiontemperature of the PPE/PS increased after curing. For the samples basedon PPE/HIPS blends, the glass transition temperature increased aftercure to a level higher than that of the thermoplastic alone. As aresult, the materials of the present invention based on PPE/HIPS blendsare capable of maintaining their stiffness and other mechanicalproperties to higher temperatures.

TABLE C Glass Transition Temperatures Ex # T_(g) (° C.) Uncured T_(g) (°C.) Cured  1C 115 12 108 128 13C 150 15 144 170 16 132 169 17 146 19 11720 142 21C 221 24C 189 213 29C 208

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand principles of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth hereinabove. All publications and patents are hereinincorporated by reference to the same extent as if each individualpublication or patent was specifically and individually indicated to beincorporated by reference.

1. A method of making a curable melt blended composition comprising meltblending at a temperature of greater than 150° C. a compositioncomprising a) 60-99 weight percent of a thermoplastic polymercomprising 1) 1-99 weight percent of a polyphenylene ether (PPE)polymer, and 2) 1-99 weight percent of a polystyrene (PS) polymer, andb) 0.1 to 40 weight percent of an uncured epoxy component comprising 1)a curable epoxy resin, and 2) a curing agent for said curable epoxyresin, wherein the epoxy component of the composition is substantiallyuncured, additionally comprising the step of applying said curable meltblended composition to a substrate as an adhesive or coating.
 2. Themethod of claim 1, wherein said thermoplastic polymer additionallycomprises greater than 0 weight percent to about 25 weight percent of acompatiblizer.
 3. The method of claim 1, wherein said curable meltblended composition comprises 70-99.9 weight percent of saidthermoplastic polymer.
 4. The method of claim 1, wherein saidpolystyrene polymer is a high impact polystyrene (HIPS) polymer.
 5. Themethod of claim 4, wherein said thermoplastic polymer comprises 10-90weight percent of said high impact polystyrene (HIPS) polymer.
 6. Themethod of claim 1, wherein said curing agent is an epoxy cure catalyst.7. The method of claim 1, wherein said melt blending step is achievedwithout addition of solvent.
 8. The method of claim 1, wherein saidcurable melt blended composition is an adhesive.
 9. The method of claim8, wherein said curable melt blended composition is an adhesive forelectronics applications.
 10. The method of claim 1, additionallycomprising the step of applying energy in the form of heat or light soas to cure said epoxy component.